Method for making interactive information devices with spacer elements

ABSTRACT

An interactive information device for use as a touch panel, touch screen, digitizer panel, or pen-input device, and a method for making such a device includes a first, transparent, electrically conductive layer supported by the rigid substrate, a flexible, transparent substrate at least partially aligned with the rigid substrate and having a second, transparent, electrically conductive layer on a surface thereof, the second conductive layer being spaced from the first conductive layer. A plurality of transparent insulating spacer members/dots are positioned on one or both of the conductive layers to allow the conductive layers to engage when the flexible substrate is pressed. The spacer members/dots comprise polymeric material including at least some inorganic material, and more preferably, comprise organic-inorganic nanocomposites having an index of refraction optically matched to the transparent, electrically conductive layer on which they are positioned.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. patent application Ser. No. 09/954,139, filedSep. 17, 2001, now U.S. Pat. No. 6,627,918 by Catherine A. Getz andMartin Mennig for SPACER ELEMENTS FOR INTERACTIVE INFORMATION DEVICESAND METHOD FOR MAKING SAME, which claims priority from U.S. ProvisionalPatent Application No. 60/234,867, filed Sep. 22, 2000, the disclosuresof which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

This invention relates to an improved technology for the separation of arigid, transparent, conductively coated substrate and a flexible,transparent, conductively coated top sheet as used in an interactiveinformation device such as a computer touch panel, a digitizer panel, apersonal digital assistant known as a PDA, or a computer pen inputdevice.

In an interactive information device having opposing conductive surfaceson a flexible top sheet and a rigid bottom sheet, “spacer dots”, or thelike, are non-conductive insulating islands or spacer elements thatseparate the transparent conductively coated rigid substrate from theflexible transparent conductively coated top sheet in a touch inputdevice when in its normal, untouched condition. When a user presses onthe top sheet, such as with a finger or stylus, the flexible transparentconductive substrate is forced to make contact with the transparentconductively coated rigid substrate creating an electrical circuit fortouch detection. When the device is not being touched, it is importantthat the flexible top sheet and the rigid back substrate do not comeinto contact so as to avoid creating a false touch. It is also desiredthat the spacer dots or elements be of minimal visibility for optimaloptical performance of the information device.

SUMMARY OF THE INVENTION

The present invention includes an improved process and improvedmaterials for producing uniformly dispersed, consistent, durable,essentially non-visible, fixed substrate-interpane-spacer elements (forexample “spacer dots”) for spacing the opposing conductive surfaces ofthe flexible top sheet and rigid bottom sheet of an interactiveinformation device.

The invention is most effectively accomplished by the application of thenon-conducting spacer dots or elements on the rigid substrate of theinteractive information device using appropriately tall dots or elementsseparating the sheets well apart for optimum electrical performance (nonfalse—touch) while minimizing visibility for optimum optical performance(such as by rendering the dots invisible such as by index matching thedot material to the surrounding interpane medium and/or by having asmall dot diameter and/or by having few, well spaced dots). It ispreferred that the performance be further improved by the use of spacerdot materials that are optically matched to the transparent conductors,typically indium tin oxide. It is preferred that the registration and/ororientation of the dots on the glass be matched to the particular touchscreen design. It is preferred that the placement of the dots on theglass allow for manufacturability of more than one touch device percoated stock sheet, known as “stock sheet” or “stock lite” formsubstrates. It is also preferred that the spacer dots be durable towithstand post-processing requirements such as washing, cutting, baking,and the like, for the manufacturing of the touch devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional, side elevation of an interactive informationdevice incorporating the improved spacer elements of the presentinvention;

FIG. 1A is a sectional, side elevation of a second embodiment of theinteractive information device of the present invention;

FIG. 1B is a sectional, side elevation of a third embodiment of theinteractive information device of the present invention;

FIG. 2 is a flow diagram of a preferred method for making theinteractive information device of FIG. 1 incorporating the presentinvention; and

FIG. 3 is a photograph of exemplary spacer elements in accordance withthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

More specifically, and as shown in FIG. 1, this invention relates to theimproved process and materials resulting in an interactive informationdevice such as a resistive touch device 60 comprising rigid substrate 10such as soda lime glass with a transparent conductive thin film 20. Thespacer dots or elements 30 are deposited most preferably by silk screenmethods on thin film 20. The flexible substrate 40 with transparentconductive thin film 50 provides the top sheet of the resistive touchdevice 60. Optionally, the transparent substrate 10 of the presentinvention may be an optical plastic comprising a conductively coatedcyclic olefin copolymer plastic substrate as disclosed in U.S. patentapplication Ser. No. 09/946,228, filed Sep. 5, 2001, entitled IMPROVEDPLASTIC SUBSTRATE FOR INFORMATION DEVICES AND METHOD FOR MAKING SAME,the disclosure of which is hereby incorporated by reference herein inits entirety. Such rigid plastic substrate may be formed from a cyclicolefin copolymer (COC) such as is available from Ticonca of Summit,N.J., under the trade name “Topas.” Cyclic olefin-containing resinsprovide an improved material for a rigid, transparent conductivelycoated substrate suitable for use in an information display. Theimproved information display incorporating the improved plasticsubstrate is lightweight, durable, flex resistant, dimensionally stableand break resistant as compared to other, more conventional substrates.A rigid plastic substrate can be formed by extrusion, casting orinjection molding. When inject on molding is used such as when forming asubstrate from a cyclic olefin copolymer (COC), a non-planar curved(spherical or multiradius) part can be formed, optionally with at leastone surface roughened (such as by roughening/patterning a surface of thetool cavity used for injection molding) so as to have a light-diffusing,anti-glare property.

A transparent, plastic substrate such as one formed from cyclic olefinpolymer resin can be used to form a rigid panel or back plate for use ina resistive membrane touch device where the cyclic olefin panelfunctions as a transparent back plate for a flexible, conductive,transparent touch member assembly as is also described in U.S. patentapplication Ser. No. 09/946,228 filed Sep. 5, 2001, incorporated byreference above.

The transparent thin film conductors 20 and 50 are typically metaloxides such as indium tin oxide, tin antimony oxide, fluorine doped tinoxide, or tin oxide. The spacer dots 30 preferably consist oforganic-inorganic nanocomposites (Nanomeres®) utilizing methyltetraethylorthosilicate, tetraethylorthosilicate, orglycidoxypropyltrimethoxysilane as network formers hydrolyzed usinghydrochloric acid prepared initially in a paste form. Silica sols,silica powders, ethyl cellulose, and hydroxypropyl cellulose may beutilized as additives to adjust viscosity. Cyracure, (Union Carbide, UV6974) serves as the photoinitiator allowing for the use of ultravioletlight for curing. The resulting improved spacer dots 30 can be enhancedoptically by nano-paricle metal oxides and pigments such as titaniumdioxide (TiO₂), barium titanium oxide BaTiO), silver (Ag), nickle (Ni),molybdenum (Mo), and platinum (Pt). The resulting index of refraction ofthe dots 30 for substantial optical matching to the transparentconductor is referably about 1.49 to about 2.0, most preferably about1.75 to about 1.95 (for light having a wavelength at the sodium D line,i.e., at about 589 nanometers).

The preferred spacer dots, such as those shown in FIG. 3, are producedby silk screen printing using fine mesh sieves with appropriate holepatterns. The nanoparticles can be used to adjust the refractive indexof the dots easily; for example, the nanoparticles can include silicondioxide for decreasing the index; or zirconium dioxide, titaniumdioxide, and tantalum pentoxide for increasing the refractive index. Thenanoparticles can be used to adjust the viscosity of the paste. Theincorporation of nanoparticles leads to reduced shrinkage during thecuring of the spacer dots. The ultraviolet (UV) curable silk screenprinting paste is preferably synthesized using a nanocomposite materialas described in U.S. Pat. No. 5,910,522 “Composite Adhesive for Opticaland Opto-Electronic Applications” by Institut fur Neue Materialiengemeinnutzige GmbH, Saarbrucken Germany, invented by Helmut Schmidt,Saarbrucken-Gudingen et al, dated Jun. 8, 1999, the entire disclosure ofwhich is hereby incorporated by reference herein. The preferredscreening paste contains the following:

a) transparent polymers and/or polymerizable oligomers and/or monomers,

b) nanoscale inorganic particles,

c) optionally, compounds for the surface modification of said inorganicparticles,

d) optionally, a crosslinking initiator.

In some forms of the invention, it may be useful to incorporate areduced glare, conductive coated panel having increased visible lighttransmission and suitable for use as a touch screen, digitizer panel orsubstrate in an information display and incorporating one or more thinfilm interference layers forming a thin film stack on opposite surfacesof a substrate such as that described herein and a transparentelectrically conductive coating on the outer most layer of one or bothof the thin film stacks, such as described in U.S. patent applicationSer. No. 09/883,654, filed Jun. 18, 2001 entitled ENHANCED LIGHTTRANSMISSION CONDUCTIVE COATED TRANSPARENT SUBSTRATE AND METHOD FORMAKING SAME, the disclosure of which is hereby incorporated by referenceherein.

The present invention may also include the use of a reduced contrast,increased transmission, conductively coated panel wherein opticalin-homogeneity is reduced between the transparent conductively coatedregions and the non-coated regions rendering these delineation regionsessentially visually indistinguishable when viewed so that there is nosubstantial contrast apparent when viewed in reflected light asdescribed in U.S. provisional patent application Serial No. 60/239,788,filed Oct. 12, 2000, entitled REDUCED CONTRAST IMPROVED TRANSMISSIONCONDUCTIVELY COATED TRANSPARENT SUBSTRATE, the disclosure of which ishereby incorporated by reference in its entirety.

The preferred process, and as shown in FIG. 2, for the application ofthe spacer dots 30 starts with the use of conventional glass cleaningtechniques for preparation of the transparent conductively coated rigidsubstrate or lite 10. The substrate is in the form known as stocksheetallowing for the subsequent cutting from and manufacture of multipletouch devices from one lite. Lites can be processed in the flat or bentproduct configuration. Prior to the deposition of the transparentconductor thin film 20, a pattern of a mask material may be applied tothe raw glass using a silk screen coating method, 325-mesh stainlesssteel screen. This allows removal of the thin film conductor, indium tinoxide for example, in the areas coated with the mask material followingthe deposition of the conductive film. The conductive thin film 20,indium tin oxide, is then deposited on surface 24 of the lite, over anymask material, preferably by the sputtering physical vapor depositiontechnique or evaporation physical vapor deposition technique. A thickfilm conductive electrode pattern, typically a silver frit such asDupont 7713, is then applied using a silk screen coating method, 325stainless steel mesh silk screen with glass frit as required based onthe touch screen design. The thin film conductor 20 and the thick filmconductor are then cured using a conventional baking process, such as480 degrees C. for 60 minutes. The thin film may be chemically reducedin an inert forming gas curing environment. Following curing of thethick film and thin film conductors, the coated lite is washed usingconventional glass washing techniques. This prepares the lite for theapplication of the spacer dots and removes residual mask material forthe deletion of specific areas of the thin film conductor as required bythe touch screen design. The transparent conductor may also be deletedin selected areas following curing using photolithography or laserdeletion methods.

The spacer dots 30 are then applied to the transparent conductor 20 onsubstrate or lite 10 using conventional silk screening techniques usinga 400-mesh stainless steel. Alternately, the dots 30 a, may be appliedto surface 51 of transparent conductor 50 or to both conductors 20 and50 as described below. The dots are arranged in an orientation based onthe design of the touch screen. Optimum design calls for dots 30 to benon-visible minimizing diameter with maximum height for electricalfunctionality. Spacer dot dimensions for width are about 125 microns toabout 15 microns, preferably about 100 microns to about 25 microns, mostpreferably about 80 microns to about 40 microns in diameter. Spacer dotdimensions for height are about 25 microns to about 3 microns,preferably about 15 microns to about 5 microns, most preferably about 12microns to about 8 microns. The spacer dots are then cured usingultraviolet light energy level of less than about 1000 mJ/cm2,preferably less than about 500 mJ/cm2, most preferably less than about400 mJ/cm2 and/or drying at less than about 300 degrees C. for less thanabout 40 minutes, preferably less than about 200 degrees C. for lessthan about 20 minutes, most preferably less than about 100 degrees C.for less than about 10 minutes. The coated lites with dots 30 thereonare then washed using conventional glass washing techniques, inspected,and cut to final touch screen dimensions using conventional glasscutting techniques. Dielectric materials and adhesives are applied tothe resulting rigid glass coated substrate. The flexible conductive topsheet 40 is then bonded to the conductive glass substrate 10 with thespacer dots 30 separating the top sheet from the coated glass substrate.A flexible electric connector is electrically connected to the completeassembly for attachment to the information device. The device is theninspected and tested electronically. The resulting product is thecomplete interactive information device 60.

Alternately, as shown in embodiment 60′ in FIG. 1A, transparent,insulating spacer members or dots 30 a, which are substantially similarto spacer dots 30 described above, may be arranged and located onsurface 51 of conductive thin film coating 50 in the same manner asdescribed above for dots 30 on surface 22 also to avoid false-touchsensing of the touch screen.

In yet another embodiment 60″, shown in FIG. 1B, spacer members or dots30 b may be located and arranged on surface 22 of conductive coating 20while spacer members 30 c may be arranged and located on surface 51 ofconductive thin film coating 50. Spacer members or dots 30 b and 30 care substantially similar to spacer members or dots 30 described above.In embodiment 60″, however, spacer dots 30 b, 30 c alternate on oppositesides of the gap on coatings 20, 50 and are spaced at greater a distancefrom one another on each of the opposing surfaces so as not to bealigned with or engage one another but allow the conductive coatings 20,50 to engage one another between the spacer dots when flexible film 40is touched or pressed.

EXAMPLE

A preferred synthesis for the spacer dot paste was produced with amixture of 118.2 g glycidoxypropyltrimethoxysilane, 13.5 g bidistilledwater and 4 g hydroxypropyl cellulose refluxed for 24 hours. The mixturewas filtered afterwards. In addition, a mixture of 10 g of 30% by weightcolloidal silicon dioxide in isopropanol and 2.4 mg 40% by weighttetrahexylammoniumhydroxide in water was produced under stirring. 20 gof glycidoxypropyltrimethoxysilane and 3 g of 30% by weight colloidalsilicon dioxide in isopropanol/40% by weight tetrahexylammoniumhydroxidein water mixture were mixed, water and alcohol were removed bydistillation (temperature at 60 degrees C., pressure at 200 mbar,removal of 25.4% of the mixture). Afterwards 2 weight percent of thephotoinitiator Union Carbide Cyracure UVI 6974 were added.

While several forms of the invention has been shown and described, otherforms will now be apparent to those skilled in the art. Therefore, itwill be understood that the embodiments shown in the drawings anddescribed above are merely for illustrative purposes, and are notintended to limit the scope of the invention which is defined by theclaims which following including the doctrine of equivalents.

What is claimed is:
 1. A method for making an interactive informationdevice comprising: providing a rigid, transparent substrate; providing afirst transparent, electrically conductive layer supported by a surfaceof said rigid substrate; providing a first flexible, transparentsubstrate having a second transparent electrically conductive layer on asurface thereof; forming a plurality of insulating spacer members bydepositing portions of a material comprising polymeric material and atleast some inorganic material at spaced locations on at least one ofsaid first and second electrically conductive layer; and securing saidfirst flexible substrate to said rigid substrate such that said firstand second electrically conductive layers on said respective substratesare at least partially aligned with one another and spaced from oneanother by a gap in which said spacer members are positioned wherebysaid flexible substrate may be flexed by pressing to engage saidconductive layers.
 2. The method of claim 1 including deleting portionsof at least one of said first and second electrically conductive layersto provide a touch screen pattern.
 3. The method of claim 1 includingforming said spacer members by silk screening said material on at leastsaid one electrically conductive layer, and curing said formed spacermembers after silk screening.
 4. The method of claim 3 including formingsaid spacer members by silk screening said material on both of saidfirst and second electrically conductive layers, and curing said formedspacer members.
 5. The method of claim 3 wherein said curing includessubjecting said spacer members to ultraviolet light.
 6. The method ofclaim 3 wherein said curing includes drying said spacer members at lessthan about 300 degrees C. for less than about 40 minutes.
 7. The methodof claim 1 wherein said forming includes substantially matching theindex of refraction of said spacer members to the index of refraction ofsaid one transparent, electrically conductive layer.
 8. The method ofclaim 1 wherein said forming of said spacer members includesincorporating nanoscale particles as said inorganic material.
 9. Themethod of claim 8 wherein said forming of said spacer members includesincorporating nano-particle metal oxides as said nanoscale particles.10. The method of claim 8 wherein said forming of said spacer membersincludes incorporating a pigment as said nanoscale particles.
 11. Themethod of claim 1 including forming said spacer members to include atleast one of a compound for surface modification of said inorganicmaterial, and a cross-linking initiator.
 12. The method of claim 1including forming said spacer members from an organic-inorganicnano-composites.
 13. The method of claim 1 wherein said forming includespreparing a paste of said material and silk screening said spacermembers onto said one electrically conductive layer from said paste. 14.The method of claim 13 including silk screening said spacer members witha mesh screen such that at least one of said spacer members has a widthdimension of at least about 15 microns.
 15. The method of claim 14including silk screening said spacer members with a mesh screen suchthat at least one of said spacer members has a height dimension of atleast about 3 microns.
 16. The method of claim 14 including silkscreening said spacer members with a mesh screen such that at least oneof said spacer members has a height dimension of about 3 microns toabout 25 microns.
 17. The method of claim 13 including silk screeningsaid spacer members with a mesh screen such that at least one of saidspacer members has a width dimension of about 15 microns to about 125microns.
 18. The method of claim 13 including silk screening said spacermembers with a mesh screen such that at least one of said spacer membershas a height dimension of at least about 3 microns.
 19. The method ofclaim 13 including silk screening said spacer members with a mesh screensuch that at least one of said spacer members has a height dimension ofabout 3 microns to about 25 microns.